How is a Water System Disinfected?
1. Pump the well or water system thoroughly until the water is clear and free from turbidity, being sure to flush out all distribution piping.
2. Pour unscented household bleach (Clorox, Purex, or other brand of regular household bleach - 5-¼% solution) directly into the well, spring or reservoir.
Do not use "stabilized" swimming pool chlorine or "Burn Out" as they are unsuitable for use in drinking water.
The disinfectant (chlorine) can be added directly into the well casing access. Do not introduce chlorine into the pump column, drop pipe or electrical conduits. Use a gallon of household bleach for every 500 gallons of water in the system. For example, you will need about ½ gallon of household bleach to disinfect a well that is 200 feet deep with a static water level of 30 feet.
3. With wells, chlorinated water can be circulated by pumping it from the well and discharging it back into the well through a hose. This serves to clean parts of the well above the water line, as well as to aid in mixing.
4. Pump the chlorinated water throughout the entire system. Do this by opening each tap until you can smell the chlorine coming through, shut off the tap and go to the next one. Leaving a line undisinfected can recontaminate a system, so be sure to flush all toilets and open every tap, including hot water and irrigation taps.
5. Allow chlorinated water to stand in the entire system for as long as possible. Overnight is adequate, but twenty-four hours is better. This gives the chlorine a chance to work on any contamination that may be in the system.
6. Flush out the entire system until the chlorine is gone. This can take several hours and it can be difficult to determine of all the chlorine has been removed. The best results are obtained with a chlorine test kit (like a swimming pool test kit). If you have a septic system, it would be advisable to discharge the water from an outside faucet. In addition, discharged water should be disposed of in areas where no harm will occur to animals, fish or vegetation.
7. Once the chlorine has been removed and it has been at least 96 hours since accomplishing the above procedures, then the water supply should be retested for bacteriological quality. Only a laboratory can determine if the water is free from contamination. It is also recommended that you do not drink the water or use it for culinary purposes during the disinfection process.
8. If the contamination is not corrected, repeat the above procedure. Please be advised that wells must be constructed so as to protect the groundwater from many surface contamination. To disinfect a well or water storage tank that is not protected from surface contamination is wasted effort.
9. In those instances not resolved by protection of the water source and repeated disinfection efforts, you may have to install an approved automatic chlorinator which continuously disinfects the water, drill a new well or connect to an approved public water supply.
If you have any questions, or if you wish to have your water supply sampled for bacteriological quality (there is a fee for this service), please contact:
Auburn Office of the Placer County Division of Environmental Health Services at (530) 745-2300
Placerville Office of the El Dorado County Environmental Management (530) 621-5300